The present invention relates to a medical electrode lead employing flexible tines to hold the distal tip of the electrode in place.
Today there are available many forms of medical electrode leads which are provided with a metallic distal tip which is placed adjacent to excitable tissue, such as the inside wall of the heart. Electric current supplied to the distal tip stimulates the muscle in contact with the tip.
There are three apparently conflicting demands placed upon the geometric configuration of such medical electrode leads. First, it is vitally important that the electrode lead have an effective anchoring configuration so that once the distal tip is correctly positioned it remains in that position. Second, the electrode lead must also be small enough and have a sufficiently smooth surface to allow for passage through tight places, such as the inside of small blood vessels, in order to reach the desired location. Third, the electrode lead must be capable of being removed from an anchored position, especially during the process of initially positioning the distal tip.
The prior art devices evidence many and varying attempts to solve these conflicts. Some employ a truncated cone section behind the distal tip with the proximal end of the cone section being used as a flange to engage body tissue such as the trabecular muscles inside the heart, with the smooth slope of the cone section minimizing trauma to the inside walls of blood vessels. (See U.S. Pat. No. 4,030,508 issued to Thalen on June 21, 1977). However, the anchoring effect of such devices is severely limited since the size of the flange is restricted by the inside diameter of the smallest vein through which the flange must pass.
There are prior art devices which employ flexible tines that extend from an electrode lead adjacent the distal tip and form an acute angle with the axis of the electrode lead. (See U.S. Pat. No. 3,902,501 issued to Citron et al. on Sept. 2, 1975). Flexible tines have also been extended from a ring which surrounds the electrode lead at a point behind the distal tip (See U.S. Pat. No. 4,033,357 issued to Helland et al. on July 5, 1977).
Provision has been made, for example in the above-mentioned Citron et al. patent, to hold tines against the electrode lead during insertion thereby reducing resistance to passage through veins. The tines are then released when the distal tip is in position. The primary disadvantage of such prior art arrangements comes from the abrupt transitions created at the base of the tines when they are in the folded configuration. Such abrupt transitions are a source of trauma to the inside walls of veins, cause increased resistance to passage of the electrode lead along the veins, and hence limit the minimum size vein through which such electrode leads may pass.
Still other prior art electrode leads employ retractable forward facing tines which are designed to be mechanically thrust into the wall of a muscle tissue and thereby hold a distal tip in place, at least for the first few days after insertion until tissue can grow around the electrode lead. (See U.S. Pat. Nos. 3,754,555 and 3,976,082 issued to Schmitt on Aug. 28, 1973 and Aug. 24, 1976 respectively). While this prior art approach has the advantage of not having any abrupt transitions present on the outside surface of the electrode lead during insertion, the mechanics required to project the tines after placement of the electrode lead are complex, costly, and subject to failure.
It is, accordingly, an object of the present invention to provide a simple electrode lead structure which minimizes resistance to insertion and yet effectively holds the distal tip of the electrode lead in position after insertion.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.